C-shaped canal system in mandibular premolars evaluated by Cone-beam computed tomography

Aim: To evaluate cone-beam computed tomography (CBCT) images to determine the presence of mandibular premolars with C-shaped canal system and to classify them. Methods: 697 CBCTs were observed, 170 of them fulfilled the selection criteria. Once established the presence of C-shaped canal system, teeth were classified according to Fan et al.’s classification. Data description was made by frequencies and percentages rates, with a 95% confidence interval (IC95) according to score method. Comparisons were assessed using the Chi-square test with a significance level equal to 5%. Results: Out of 158 patients with mandibular first premolars, 21 showed C-shaped canal system (13%; IC95: 9% to 19%), and of 142 patients with mandibular second premolars, 4 presented C-shaped canal system (3%; IC95: 1% to 7%).Out of 17 patients presenting both first premolars, 6 showed a bilateral pattern (35%; IC95: 17% to 59%) and 11 presented an unilateral pattern (65%; IC95: 41% to 83%). When the condition was unilateral (n = 15), 7 patients showed C-shaped canal in tooth 3.4 (47%; IC95: 25% to 70%) and 8 showed C-shaped canal in tooth 4.4 (53%; IC95: 30% to 75%). 4 second premolars showed C-shaped canal and the condition was unilateral for all of them. As far as axial plane was concerned for the first premolars, in the coronal third prevailed the C4c configuration (81%; IC95: 63 to 92%), in the middle third C3 (56%; IC95: 37% to 72%), and in the apical third C3 and C4b in the same percentage (19%; IC95: 8 a 37%). For the second premolars, in the coronal third prevailed the C4c configuration (75%), in the middle third C3 (75%) and in the apical third C5 (50%). Conclusion: The present study contributes to the epidemiological knowledge about an anatomical variable of the inner dental configuration and its extrapolation to clinical practice.